This research proposal is an experimental investiation into: (1) the identification of synaptic transmitter actions on neurons in the vertebrate retina; (2) the ionic mechanisms which underly cell communication between neurons and glia; (3) the neuronal pathways which underly ganglion cell receptive field organization and (4) the ionic activity changes which result from intercellular communication in the vertebrate retina. This study will be carried out in isolated mammalian and amphibian retina-eyecup perparations. Intracellular recording experiments will be conducted, while the external environment is modified by alteration in ionic constituents, transmitter agents and transmitter antagonists. Ion-selective microelectrodes will be used to measure intracellular ionic activity and the modifications in ionic concentrations which result from synaptic communication. These studies will determine the functional organization of the retina, the chemical basis of communication and the neuronal pathways which are reflected in the electroretinogram.